Because the net effect is that it makes your influence proportional to your amount of money, which is already an issue nowadays. You may as well call for census suffrage.

Not unless you were trying to pass something so wildly unpopular that literally everyone would've voted against it otherwise. Most issues have at least a few people voting for each side, so you just need to add enough to get tip it in your favor. Sometimes just 20k votes would do it - that much would've probably swung the Colorado gubernatorial election this week.

Significantly less, and experience from my country shows that it is unfortunately a profitable business model. Basically, by buying national media for dimes (as there is crisis of print), you can get enough power to direct sums of money two orders of magnitude larger.

Buy newspapers and TVs for hundreds of millions, control tens of billions...